Packages which, when sealed, permit gas to pass back and forth between the interior and exterior of the package yet are impermeable to the passage of bacteria, are used in a wide variety of ways for many purposes. Typically, all or a portion of such a package is constructed of a microporous member which permits passage of gas but not bacteria.
According to one variation, the package is either sealed and then sterilized or sterilized and then sealed under sterile conditions. Such sealed, sterilized packages are particularly useful for the collection of biological, marine, agricultural, and other samples for later analysis at a location remote from the collection site. This is accomplished by opening the sterilized package, inserting the sample, and immediately resealing the package in a manner as will preclude the entry of foreign matter which would introduce unknown qualitative and quantitative variables into the subsequent analysis. The object is to preserve the sample in a condition in which its subsequent laboratory analysis will be meaningful insofar as ascertaining accurately its state at the time of collection. Thus, if the sample was originally bacteria-free, the object is to preserve it in a bacteria-free condition. If the original sample contains bacteria, the object is to prevent contamination with other bacteria. See U.S. Pat. No. 3,819,106, the entire disclosure of which is incorporated herein by reference.
In another variation, nutrient material such as for example soil, grain, agar-agar culture medium, or gelatin culture medium, is placed in a package and the unsealed package and its contents are sterilized. Following sterilization the nutrient medium is inoculated with one or more bacteria or one or more fungi (e.g., mushroom mycelium) and the package is sealed under conditions such that contamination with foreign bacteria is avoided. The package is then stored under incubation conditions for growth of the inoculating organism or organisms. During incubation, the package excludes foreign bacteria, but permits gases such as oxygen, carbon dioxide, and water vapor to pass through the package. In a modification of this variation, nutrient material is placed in the package and then the package is sealed and sterilized. After sterilization the package is opened, inoculated with the desired organism or organisms, and resealed. Inoculation and resealing are accomplished under conditions such that contamination by foreign bacteria is avoided. Storage under incubation conditions then proceeds as earlier described. See U.S. Pat. No. 4,063,383, the entire disclosure of which is incorporated herein by reference.
Perhaps the most frequent use of packages of this type is the packaging of medial items such as scalpels, forceps, clamps, syringes, hypodermic needles, catheters, prostheses, pins, suture materials, gauze, dressings, bandages, sponges, and the like, although various other items may be so packaged. Hardware for inclusion in interplanetary probes would be an example of the latter category of items.
In one variation, the package is sterilized, the sterilized item is placed in the package, and the package is sealed. Placement in the package and sealing are accomplished under conditions that prevent contamination from foreign bacteria.
In another variation, the item to be protected from bacteria is placed in the package and then the package is sealed, and sterilized. Such sealed, sterilized packages can be stored for substantial periods of time while the contents are maintained in a bacteria-free condition. Sterilization is most often performed by either the packager who is frequently the manufacturer of the item, or by the user of the item such as a hospital or clinic.
The principle upon which all of the above uses are based is that the package, when sealed and sterilized in a sterilizing environment before or after sealing, maintains the interior of the package in a bacteria-free condition after removal of the package from the sterilizing environment.
The impermeability to the passage of bacteria and the permeability to the passage of gases between the interior and exterior are characteristics of the sealed package which permit a wider variety of uses and sterilization processes than would be the case if such characteristics were not present.
The three methods of sterilization most commonly used are steam autoclaving, exposure to ethylene oxide gas, and exposure to ionizing radiation such as gamma radiation. As indicated in U.S. Pat. No. 4,352,429, the entire disclosure of which is incorporated herein by reference, the choice of materials is largely dependent on the method of sterilization to which the package will be subjected.